The present invention relates in general to a retractor for a seat belt assembly for use on motor vehicles, and more specifically to a seat belt retractor of the emergency locking type. The emergency locking retractor according to the invention responds to rapid extension of a webbing or strap, although it admits of ready adaptation for response to the acceleration or deceleration of the vehicle or the like as well.
Emergency locking retractors have been known and used extensively for vehicular seat belt assemblies. They incorporate a locking mechanism that is activated by vehicle accleration, webbing movement relative to the vehicle, or other automatic action during an emergency. When the vehicle is at a standstill, or travelling at accelerations of, say, not more than 0.3 G, the emergency locking retractor should allow the webbing or strap to be extended and retracted freely as required by the bodily movement of the wearer. In the event of rapid braking, collision, rollover, or other abnormal conditions of the vehicle, the retractor should immediately lock up to prevent any further extension of the webbing for the safety of the user.
Being installed in narrowly confined spaces within motor vehicles, the emergency locking retractors should be of minimal dimensions. They should nonetheless be positive, reliable and fast-acting in operation and trouble-free in construction.
There has been another problem seriously affecting the utility of known emergency locking retractors of the type sensitive to webbing movement relative to the vehicle. Upon full retraction of the webbing, by the force of a spring acting on the webbing reel, the webbing sensor of some conventional retractors has been prone to activate the locking mechanism accidentally. This makes impossible, or at least difficult, the ready re-extension of the webbing.